//      https://ac.nowcoder.com/acm/problem/222104


#include <iostream>
#include <string>
using namespace std;

int n, s[30];
char c;

int main()
{
    cin >> n;
    for (int i = 0; i < n; i++)
    {
        cin >> c;
        s[c - 'a']++;
    }

    int num = 0, cnt = 0;
    for (int i = 0; i < 26; i++)
    {
        if (s[i] > num)
        {
            num = s[i];
            cnt = i;
        }
    }

    if (2 * num > n + 1)
        cout << "no" << endl;
    else
    {
        cout << "yes" << endl;
        n -= num;
        string ans;
        while (num--)
        {
            ans += (char)(cnt + 'a');
            for (int i = 0; i < 26 && n >= num; i++)
            {
                if (i != cnt && s[i])
                {
                    s[i]--;
                    ans += (char)(i + 'a');
                    n--;
                }
            }
        }
        cout << ans << endl;
    }

    return 0;
}